In vehicles an electric motor is used both as a starting motor and for driving of other parts of the vehicle, such as an AC (air condition), fans and water pumps. In some situations the electric motor is driven as a generator. This is used in hybridizing in that energy is stored during braking, which stored energy can be used during acceleration. A driveline comprising the electric motor and the engine (internal combustion engine) of the vehicle is normally formed. A gearbox of this driveline is normally placed adjacent to the engine.
In some instances it is beneficial to be able to run the AC even if the engine of the vehicle is turned of Such an instance is if one wants to cool down the interior of the vehicle before entering it.